1. Field of the Invention
The present invention relates to a semiconductor manufacturing apparatus and, more particularly, the present invention concerns a semiconductor manufacturing apparatus for processing the surface of a semiconductor substrate using a reactant gas, the processing including etching and film formation.
2. Description of the Related Art
FIG. 1 is a schematic view of a conventional semiconductor manufacturing apparatus. A semiconductor substrate 2 fixed to a holder 3 is disposed within a generally cylindrical chamber 1. A reactant gas supplied to the interior of the chamber 1 through a gas supply pipe 4a from a gas supply port 4, flows within the chamber 1 in the directions indicated by arrows 6, and then reaches the surface of the substrate 2. The reactant gas which has not been used for reaction is discharged to the outside of the chamber 1 from a discharge port 5. A valve for controlling the amount of exhaust, e.g., an exhaust automatic adjusting valve 7, is provided in an exhaust pipe 7a connected to the discharge port 5.
The thus-arranged conventional semiconductor manufacturing apparatus will be operated in the manner described below. First, the substrate 2 is set on the holder 3 within the chamber 1. Next, after the interior of the chamber 1 has been filled with an inactive gas such as N.sub.2, a reactant gas is supplied into the chamber 2 from the gas supply port 4 at a predetermined flow rate. A mixture of HF gas and N.sub.2 gas may be used as a reactant gas. If the process is etching, the reactant gas is used an etching gas. At this time, the pressure in the chamber 1 is continuously detected by a sensor (not shown) so that the interior of the chamber 1 can be maintained at a predetermined pressure by the exhaust automatic adjusting valve 7. After the passage of a predetermined time, a substituting gas, e.g., N.sub.2 gas or air, is supplied from the gas supply port 4 to substitute for the reactant gas remaining in the chamber 1. The reaction of the reactant gas that takes place on the surface of the substrate 2 starts immediately after the supply of the reactant gas into the chamber 1, and continues until the discharge thereof by the supply of the substituting gas. The substrate 2 is taken out of the chamber 1 after the reactant gas has been completely discharged out of the chamber 1.
In the thus-arranged semiconductor manufacturing apparatus, since the chamber 1 is provided with only one gas supply port for supplying the reactant gas and the substituting gas as well as only one discharge port 5 for discharging the gases, the reactant gas may flow within the chamber 1 at a non-uniform flow rate or in non-uniform directions, depending on the overall shape of the chamber 1, the mounting positions of the gas supply port 4 and the exhaust port 5 and so on. This non-uniformity of the flow rate and the direction of the reactant gas varies the amount of reactant gas that reaches the surface of the substrate 2, making highly accurate processing of the surface of the substrate 2 impossible.